fix: docker-publish workflow failing on main due to inexisting ARCH env var (#431)

Author: micmarty-deepsense

Diff for: .github/workflows/docker-publish.yml

@@ -90,7 +90,7 @@ jobs:
     - name: Test image
       run: |
         source .venv/bin/activate
-        export DOCKER_IMAGE="$DOCKER_BUILD_REPOSITORY:$ARCH-$SHORT_SHA"
+        export DOCKER_IMAGE="$DOCKER_BUILD_REPOSITORY:${{ matrix.arch }}-$SHORT_SHA"
         if [ "$DOCKER_PLATFORM" == "linux/arm64" ]; then
           SKIP_INFERENCE_TESTS=true make docker-test
         else